Wavelength Division Multiplexing (WDM) and Dense Wavelength Division Multiplexing (DWDM) are technologies that enable a multitude of optical wavelengths of differing frequencies to be transported over a single optical fiber. A DWDM network is constructed by interconnecting multiple DWDM network elements. Each network element typically contains functions such as optical multiplexing equipment (filtering), optical de-multiplexing equipment (filtering), optical amplifiers, optical power monitors, optical supervisory channel processors, network element control processors, and optical converters. In existing DWDM network elements, each individual function within the network element was placed on individual circuit packs. Each circuit pack then had to be plugged into a common backplane which supplied power and control to each circuit pack. In order to construct a working DWDM network element, many of the circuit packs had to be further interconnected with one another using optical cables which often attached to the front panels associated with the circuit packs.
In addition to the specific functional circuitry on each circuit pack, each circuit pack contained circuitry and mechanical structures that were common to (i.e., repeated on) each circuit pack. For instance, each circuit pack would commonly contain a power supply circuit, a control or communication circuit, an electrical backplane connector, a mechanical front panel, one or more optical front panel connectors (used to interconnect optical oriented circuit packs to one another), and optical power monitoring circuitry.
Furthermore, since the surface area on any given circuit pack front panel was limited, some circuit packs had to contain high-density parallel optical connectors in order to accommodate the high number of interconnects associated with a given circuit pack. The parallel optical connectors required the use of complex adaptation cables (break-out cables), or external optical patch panels in order to convert the high-density optical connections to individual connections usable by other optical circuit packs.
The combination of the plurality of differing circuit packs, the plurality of optical connections between circuit packs, and the plurality of optical adaptation cables and optical patch panels, resulted in a DWDM network element that was difficult and error prone to install. Furthermore, optical power monitoring circuitry was required throughout the system in order to verify that the optical interconnect cables (interconnecting the various functional circuit packs) were connected to their proper points within the system.
Therefore, it can be seen that in order to lower the cost and simplify the installation of a DWDM network element, what is needed is a method of constructing a DWDM network element that eliminates much of the repeated common circuitry and mechanics on circuit packs, and eliminates many of the external optical interconnect cables, adaptation cables, and optical patch panels.